Changing the operation of Skyrail-ITM from automatic to manual control may have disabled protection devices, causing a cable car cabin to plunge to the ground, an expert said.

Although the government refused to disclose the full reason behind the June 11 blunder, the acting deputy director of the Electrical and Mechanical Services Department, Chan Fan, said acceleration or deceleration of cable cars should normally be controlled by computer, but during the incident it was switched to manual operation. 'Someone was found to have breached the Aerial Ropeway (Safety) Ordinance ... while conducting an emergency brake test that night.'

Edmund Leung Kwong-ho, former president of the Hong Kong Institution of Engineers, said: 'Like a vehicle, when you turn off the Automatic Braking System, the speed can go as high as the machine allows, but you stand the risk of it spinning out of control.'

The Department of Justice issued three summonses on Monday against an operations employee for negligence in performing a brake test, failing to consult the manufacturer of the Ngong Ping 360 before performing the test and negligence in supervising it.

The offences carry a maximum fine of HK$10,000 and up to six months' imprisonment.

According to the report, the government conducted more than 132 inspections during the cable car's nine months of operation and advised the cable car's operator on 47 points.

Among the 22 major service disruptions during that time, half were found to be caused by poor operation and works co-ordination.

Not only was premature rusting found in major components only one year after operation, but on some occasions staff found that a part in need of replacement was out of stock.